In the preparation of polyurea and polyurethane-urea polymers, there are many polyfunctional compounds which are indicated to be useful as chain extenders, including diols and aromatic diamines. None of these compounds has a reactivity such as to make it universally ideal, and many fail to provide satisfactory properties in the products made by their use. Thus, there is still a need to find compounds capable of serving as chain extenders or curing agents. U.S. Pat. No. 4,806,616 teaches the use of certain N,N′-dialkylphenylenediamines as chain extenders in preparing polyurethanes and polyureas. In this connection, also see for example U.S. Pat. No. 4,528,363, which teaches the use of secondary aliphatic diamines as part of a resin binder, and U.S. Pat. No. 6,218,480 B1, which discloses use of aromatic diamines as hardeners for polyurethane-ureas.
Polyurethane, polyurea, and polyurethane-urea polymers are used in spray coatings and in reaction injection molding. Spray coatings find application in concrete coatings, building coatings, secondary containment coatings, parking deck coatings, moisture seal coatings, blast abatement coatings, roof coatings, bridge coatings, tunnel liners, pipe liners, manhole liners, truck bed liners, and the like. Reaction injection molding finds application in making body parts for automobiles, recreational vehicles, and farm equipment. In this connection, there is a need for a spray system incorporating a mixture of chain extenders which provides coatings that have acceptable physical properties via formulations having appropriate gel times. Similarly, there is a need for a reaction injection molding process incorporating a mixture of chain extenders which provides a reaction injection mixture that has an appropriate gel time, has suitable properties at demolding, and has acceptable physical properties.